Why Do We Have Seasons?
Earths Rotation
-the earth rotates on its axis every 23 hours and 56 minutes. -one day on Earth is one rotation of the Earth. -day on Earth is when our side of the Earth faces the sun. -night on Earth is when the side of the Earth we are on faces away from the sun. Earths Revolution -it takes about 365 days or rotations to travel or revolve around the sun once. -this is called a year. Why do We Have Seasons? -Earths orbit around the sun is NOT s perfect circle. It is an ellipse. -seasons are not caused by how close the Earth is to the sun. -in fact, the Earth is closest to the sun around January 3 and farthest away from the sun around July 4. -seasons are the result of the tilt of the Earths axis. -Earths axis is tilted 23.5 degrees. -this tilting is why we have SEASONS like fall, winter, spring, summer -the number of daylight hours is greater for the hemisphere, or half the Earth that is tilted toward the sun. -SUMMER is warmer than winter (in each hemisphere) because the Suns rays hit the Earth at a more direct angle during summer than during winter. -also the days are much longer than the nights during the summer. -during the WINTER , the Suns rays hit the Earth at an extreme angle, and the days are very short. Theses effects are due to the tilt of the Earths axis. |
Solstices
-Solstices occur twice a year, when the tilt of the Earths axis is oriented directly towards or away from the sun, causing the sun to appear to reach its northernmost and southernmost extremes. -winter solstice is the shortest day of the year. in the northern hemisphere, it occurs on December 21 and marks the beginning of winter. -the summer solstice is the longest day of the year. it occurs on June 21 and marks the beginning of summer. -during the winter the Northern hemisphere day last fewer than 12 hours and the Southern hemisphere lasts more than 12 hours. -during the winter solstice , the North Pole has a 24-hour night and the South Pole has a 24-hour day. -sunlight strikes the Earth most directly at the Tropic of Capricorn. Equinoxes -a day lasts 12 hours and a night lasts 12 hours at all latitudes. -Equinox literally means "equal night". -sunlight strikes the Earth most directly at the equator. -this occurs twice a year. Equinox -the vernal (spring) equinox occurs March 21. -the autumnal (fall) occurs on September 21. The earths seasons are not caused by the differences in the distance from the sun throughout the year. |
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